Initially, recruits without higher education or college degrees will hold the pay grade of E-1 and will be elevated to E-2 usually soon after basic training. Different services have different incentive programs for enlistees, such as higher initial ranks for college credit, being an Eagle Scout and referring friends who go on to enlist as well. Participation in DEP is one way recruits can achieve rank before their departure to basic training.
Personnel may be posted to bases in their home country or overseas, according to operational need, and may be deployed from those bases on exercises or operations anywhere in the world. During peacetime, when military personnel are generally stationed in garrisons or other permanent military facilities, they mostly conduct administrative tasks, training and education activities, technology maintenance, and recruitment.

Prospective service members are often recruited from high school or college, the target age ranges being 18–35 in the Army, 18–28 in the Marine Corps, 18–34 in the Navy, 18–39 in the Air Force and 18–27 (up to age 32 if qualified for attending guaranteed "A" school) in the Coast Guard. With the permission of a parent or guardian, applicants can enlist at age 17 and participate in the Delayed Entry Program (DEP), in which the applicant is given the opportunity to participate in locally sponsored military activities, which can range from sports to competitions led by recruiters or other military liaisons (each recruiting station's DEP varies).
The military organization is characterized by a strict hierarchy divided by military rank, with ranks normally grouped (in descending order of authority) as officers (e.g. Colonel), non-commissioned officers (e.g. Sergeant), and personnel at the lowest rank (e.g. Private Soldier). While senior officers make strategic decisions, subordinated military personnel (soldiers, sailors, marines, or airmen) fulfil them. Although rank titles vary by military branch and country, the rank hierarchy is common to all state armed forces worldwide.
The primary reason for the existence of the military is to engage in combat, should it be required to do so by the national defence policy, and to win. This represents an organisational goal of any military, and the primary focus for military thought through military history. How victory is achieved, and what shape it assumes, is studied by most, if not all, military groups on three levels.
The IRT model underlying ASVAB scoring is the three-parameter logistic (3PL) model. The 3PL model represents the probability that an examinee at a given level of ability will respond correctly to an individual item with given characteristics. Specifically, the item characteristics represented in the 3PL model are difficulty, discrimination (i.e., how well the item discriminates among examinees of differing levels of ability), and guessing (i.e., the likelihood that a very low ability examinee would respond correctly simply by guessing).
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